b***m
发帖数: 2112 | 1 昨天刷Twitter看到的文章，标题很骇人。。。我英语太烂，愣是没看明白，大家来看
看 吧^_^
原文在这里：
https://www.newscientist.com/article/dn28246-physics-of-falling-says-
professional-athletes-are-running-wrong/
文中附带了一个Journal paper的link，我这下不下来。能下载的大侠帮帮忙download
一下？谢谢先~
http://rspa.royalsocietypublishing.org/content/471/2181/2015028
Physics of falling says professional athletes are running wrong
By Rebecca Boyle
Runners may be doing it all wrong. A slightly different posture could let
runners and walkers get a gravity-driven boost – and potentially break
world records.
To most runners and coaches, running is a series of jumps, says Svein Otto
Kanstad, a physicist and former competitive runner based in Volda, Norway.
Gravity isn’t considered helpful, because its force is perpendicular to the
direction a runner is moving. But this mindset neglects the concept of
angular momentum, Kanstad says. Rather than thinking of running as a series
of jumps – leaping off one foot and landing again on the other – runners
should view their sport as a series of falls, aided by gravity, he says.
“We are falling forward, and our legs catch us,” he says. With each
footfall a runner’s body actually rotates forward, pivoting on the foot in
contact with the ground. “It is not a series of jumps, it is a series of
rotations.”
A hula hoop illustrates how this rotation provides angular momentum. If you
simply throw a hula hoop vertically into the air, it will fall flat when it
lands. But if you spin the hoop as you launch it, it will roll away after it
hits the ground because it has angular momentum.
“We are clever at using angular momentum without really knowing that’s
what we’re using,” he says. But for many runners there is room for
improvement.
Best foot forward
As a runner’s hips rotate to bring each leg forward, he or she gains
angular momentum. But most runners don’t make the best use of this. At the
moment their leading leg hits the ground, the second leg is usually
stretched out behind. In Kanstad’s revised gait, the second leg will
already have rotated forward again before the leading leg hits the ground.
By doing this, the runner’s centre of mass is tilted far forward allowing
for more forward momentum, but the recovery leg is there to stop a fall.
It’s tricky to do, but Kanstad has taught himself to run this way. He says
that retired US sprinter Michael Johnson – who has held the world record in
the men’s 400 metres since 1999 – uses the same technique.
“The arms become very important as a counterbalance to the leg movement,”
says Kanstad. “You have to change to almost opposite the way you are used
to using your arms and legs.”
He trained distance runners from Tromsø to run using this technique on
treadmills, while using straps that anchored them to the ceiling in case
they fell. In one test, a male sprinter running at 14 kilometres per hour
was making an energy saving of 10 per cent compared with his usual gait, as
measured by his consumed oxygen volume per minute. As he ran, he shouted, “
I’m flying!” Kanstad says.
Kanstad believes training distance runners and sprinters to run in this
fashion would shave minutes off race times, resulting in a rash of new
records.
“Gravity is there, and it drives us forward, but we immediately kill it by
the way we run,” he says. “Just by not being that killer, you can have 10
per cent more energy for free.” |
